I knew somebody was going to bring up the disgusting possibility of Mass Harm. Luckily, that's not an issue in my game, as Harm has been nerfed. 
As for researching new spells: it's a neat idea for a wiz, but I play a sorcerer. I've already got Haste and Fly on my list. If "Massness" comes packaged as a feat, then I don't have to fill up my higher-level slots with redundant spells, and I don't have to burn the whole day's worth of 3rd-level slots just so the party can fly across a chasm.

As for researching new spells: it's a neat idea for a wiz, but I play a sorcerer. I've already got Haste and Fly on my list. If "Massness" comes packaged as a feat, then I don't have to fill up my higher-level slots with redundant spells, and I don't have to burn the whole day's worth of 3rd-level slots just so the party can fly across a chasm.